This is an objection that you will likely encounter as you reach out to suppliers.
And it can be hard to overcome. This is mainly due to suppliers having resellers that do not actually sell anything - main thing you have to reiterate is why you won’t just be another reseller that does nothing.
Best way to overcome is a trial basis! If you are able to get them on the phone would be best but the main points you want to construct on the email response or phone call is as follows:
Thank them for the email.
Ask them for a 90 day trial - if at the end of the 90 days they are not happy with the revenue you can drive then they can end the relationship no harm no foul.
Worst case scenario is they get extra revenue they wouldn’t have had prior.
CTA: Ask for the 90 day trial again! This is done best on the phone - if you construct this on email keep it between 5-6 sentences max.